1. Field of the Invention
This invention relates to a stencil discharging apparatus in a stencil printing machine in which a stencil wound on the rotary cylindrical drum is removed with a stencil discharging claw which is provided near the outer cylindrical surface of the drum in such a manner that the claw is movable to and from the outer cylindrical surface of the drum, and the stencil thus removed is conveyed to a used-stencil accommodating section by conveying means, where it is discarded.
2. Description of the Related Art
A stencil discharging apparatus in a stencil printing machine in which a stencil paper wound on the rotary cylindrical drum is removed with a stencil discharging claw, and the stencil thus removed is conveyed to a used-stencil accommodating section by a pair of stencil conveying rollers, is known in the art. It has been disclosed, for instance, by Unexamined Japanese Utility Model Publication No. 3266/1983 and Examined Japanese Utility Model Publication No. 18867/1992.
In the above-described conventional stencil printing machine, stencil presence or absence detecting means is provided on a conveying path along which a used stencil is conveyed to the used-stencil accommodating section, to determine whether or not a stencil is present on the conveying path. That is, the stencil presence or absence detecting means determines whether or not the detecting state of the stencil presence or absence detecting means is changed to a stencil presence state from a stencil absence state within a predetermined period after the provision of a stencil discharging operation start instruction. When it is determined that the stencil absence state is switched over to the stencil presence state within the period of time, it is permitted to perform the following operation; and when not, it is decided that the stencil is removed in an unacceptable manner, and it is inhibited to perform the following operation. In addition, the detecting means determines whether or not its detecting state is changed to the stencil absence state within a predetermined period of time after being changed to the stencil presence state. When it is determined that the stencil presence state is switched over to the stencil absence state within the predetermined period of time, it is permitted to perform the following operation; and when not, it is decided that the stencil has been removed in an unacceptable manner, and it is inhibited to perform the following operation.
In the above-described conventional stencil discharging apparatus, the stencil presence or absence detecting means, which is provided on the used-stencil conveying path, is located near the pair of used-stencil conveying rollers. More specifically, the position of the stencil presence or absence detecting means corresponds substantially to the middle of the width of the used stencil which is conveyed. Hence, when the used stencil has passed through the position, then it is decided that the used stencil paper has been discharged, and it is permitted to start the following operation.
In general, in the case where a used stencil is discarded by the stencil discharging apparatus, all the surface of the used stencil which is in contact with the rotary cylindrical drum is not stained with printing ink. That is, in the case of a stencil paper made up of a thermoplastic resin film and a porous support, all the surface on the porous support side is not stained with printing ink. More specifically, only its part corresponding to the ink passage region of the rotary cylindrical drum is stained with printing ink, and the remaining part surrounding the part is not.
The used stencil paper is folded like a meander, and accommodated in the used-stencil accommodating section this case, the part of the used stencil which has been stained with print ink is held folded by the adhesion of the ink. On the other hand, both side portions of the used stencil as viewed in the stencil discharging direction, which are not stained with printing ink, are not held folded; that is, they are gradually unfolded. In the case where the used stencil conveying means is made up of a pair of rollers, sometimes the stencil may be protruded from both ends of the rollers towards the rotary cylindrical drum.
The protrusion of the stencil is gradually spread from both ends of the pair of rollers towards the center as the number of used stencils is increased in the used stencil accommodating section. When the protrusion reaches a range where the stencil presence or absence detecting means can detect the protrusion, the protrusion is actually detected; that is, it is decided that the stencil has been removed in an unacceptable manner, and the decision is notified to the operator to allow him to deal with the trouble. However, the stencil which has been jammed to this extent cannot be removed without use of the operator's hand; that is, it is necessary for the operator to pull the stencil out of the rollers with his fingers. Hence, the operator's fingers are stained with the printing ink, and at worst the stencil paper is torn into pieces, some of which may be left between the rollers.